全文获取类型
收费全文 | 95篇 |
免费 | 5篇 |
专业分类
化学 | 76篇 |
力学 | 2篇 |
数学 | 9篇 |
物理学 | 13篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 1篇 |
2012年 | 6篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 31 毫秒
91.
In the present study, a simple, rapid and precise liquid chromatographic method was developed and validated for the simultaneous determination of glimepiride and metformin in sustained release formulation. The separation was achieved on a Nucleosil 100-5SA column, 250 × 4.6 mm i.d., 5 μm using a mobile phase composed of 1.7 % ammonium dihydrogen phosphate buffer pH 3.0: acetonitrile (70:30 v/v).The instrumental settings were a flow rate of 1.0 ml min?1 and a detector wavelength of 230 nm. The retention time of glimepiride and metformin were 5.1 and 11.3, respectively. The developed method was validated in terms of specificity, sensitivity, linearity, range, accuracy, precision and ruggedness. The proposed method was successfully applied to the sustained release pharmaceutical dosage form for the simultaneous determination of glimepiride and metformin without any interference by excipients. 相似文献
92.
Acetanilide palladacycle: an efficient catalyst for room‐temperature Suzuki–Miyaura cross‐coupling reaction
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Anindita Dewan Zenith Buragohain Manoj Mondal Gayatri Sarmah Geetika Borah Utpal Bora 《应用有机金属化学》2014,28(4):230-233
The catalytic activity of three acetanilide palladacycles derived from easily accessible and commercially available acetanilide derivatives, viz. N‐phenylacetamide ( L1 ), N‐(4‐chlorophenyl)acetamide ( L2 ) and N‐(4‐methylphenyl)acetamide ( L3 ) has been examined in Pd‐catalyzed Suzuki–Miyaura reaction of arylboronic acid with aryl bromides at room temperature. The complex 1L3 exhibited efficient activity in the Suzuki–Miyaura reaction (up to 99% isolated yield) under mild reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
93.
Smita Shah S.S. Ranade S.R. Kasturi R.S. Phadke S.H. Advani 《Magnetic resonance imaging》1982,1(1):23-28
Pulsed nuclear magnetic resonance studies have been carried out on bone marrow of normal human subjects and patients with leukemia: chronic myeloid leukemia (CML) and acute myeloid leukemia (AML). It was observed that the proton spin-lattice relaxation time (T1) value was discriminatory in the normal and leukemic cases with a statistical significance of (p < 0.01). Ouabain treatment of cells did not show any perceptible change of T1 value when compared with the nontreated cells, indicating that the concomitant cation effluxes do not affect spin-lattice relaxation time. The water contents of normal, leukemic, and ouabain treated cells were in the range 60%–80%. Higher Fe levels were encountered in the normal than the leukemic samples, while levels of Zn, Cu, Mn, Co, and Ni were elevated in the leukemic samples compared with the normals. Despite the T1 differences observed, the multiparameter studies do not uniquely pinpoint factors responsible for the elevation of T1 in the malignant state. 相似文献
94.
Mridula?Sharma Gayatri?Sharma Beena?Agrawal C.?L.?Khandelwal P.?D.?SharmaEmail author 《Transition Metal Chemistry》2005,30(5):546-551
The kinetics of electron transfer from mannitol to hexacyanoferrate(III), catalyzed by osmium(VIII), has been studied in alkaline medium. The substrate order is complex, whereas it is one with respect to the catalyst. The rate is independent of the concentration of oxidant. Also, the rate increases with increasing concentration of hydroxide ion in a complex manner. A kinetic rate law corresponding to the proposed mechanism has been suggested as follows:
where [Mtol] is for mannitol. The kinetic parameters have been evaluated and the value of K1 is in agreement with the value determined spectrophotometrically. 相似文献
95.
Neeraj Soni Shivendra Singh Shubham Sharma Gayatri Batra Kush Kaushik Chethana Rao Navneet C. Verma Bhaskar Mondal Aditya Yadav Chayan K. Nandi 《Chemical science》2021,12(10):3615
The structure–function relationship, especially the origin of absorption and emission of light in carbon nanodots (CNDs), has baffled scientists. The multilevel complexity arises due to the large number of by-products synthesized during the bottom-up approach. By performing systematic purification and characterization, we reveal the presence of a molecular fluorophore, quinoxalino[2,3-b]phenazine-2,3-diamine (QXPDA), in a large amount (∼80% of the total mass) in red emissive CNDs synthesized from o-phenylenediamine (OPDA), which is one of the well-known precursor molecules used for CND synthesis. The recorded NMR and mass spectra tentatively confirm the structure of QXPDA. The close resemblance of the experimental vibronic progression and the mirror symmetry of the absorption and emission spectra with the theoretically simulated spectra confirm an extended conjugated structure of QXPDA. Interestingly, QXPDA dictates the complete emission characteristics of the CNDs; in particular, it showed a striking similarity of its excitation independent emission spectra with that of the original synthesized red emissive CND solution. On the other hand, the CND like structure with a typical size of ∼4 nm was observed under a transmission electron microscope for a blue emissive species, which showed both excitation dependent and independent emission spectra. Interestingly, Raman spectroscopic data showed the similarity between QXPDA and the dot structure thus suggesting the formation of the QXPDA aggregated core structure in CNDs. We further demonstrated the parallelism in trends of absorption and emission of light from a few other red emissive CNDs, which were synthesized using different experimental conditions.Herein we unveil the presence of a molecular fluorophore quinoxalino[2,3-b]phenazine-2,3-diamine (QXPDA) in a colossal amount in red emissive CNDs synthesized from o-phenylenediamine, a well-known precursor molecule used for CND synthesis. 相似文献
96.
A comparative study is described of the use of N-benzoyi-o-tolyl-, N-benzoyl-m-tolyl, N-benzoyl-p-tolyl-, N-benzoyl-p-chlorophenyl- and N-phenylacetylphenyl-hydroxylamines, as spectrophotometric reagents for the determination of vanadium, after extraction with chloroform. All the reagents form 1:2 (metal:reagent) complexes in hydrochloric acid media or at pH 4.8–6.0; the dissociation constants of the complexes are of the order of 10-9 and 10-8, respectively, except those of N-benzoyl-p-chloro-phenylhydroxylamine which are of the order of 10-8 in both media. The reactions in hydrochloric acid media are more selective and sensitive than those at pH 4.8–6.0. In presence of alcohol, the wavelengths of maximum absorption decrease. The pKa values of the hydroxylamines were determined in water and in alcohol-water (1:1) solutions. 相似文献
97.
Ratna S. Phadke 《Applied biochemistry and biotechnology》2001,96(1-3):279-286
A relentless decrease in the size of silicon-based microelectronics devices is posing problems. The most important among these
are limitations imposed by quantum-size effects and instabilities introduced by the effects of thermal fluctuations. These
inherent envisaged problems of present-day systems have prompted scientists to look for alternative options. Advancement in
the understanding of natural systems such as photosynthetic apparatuses and genetic engineering has enabled attention to be
focused on the use of biomolecules. Biomolecules have the advantages of functionality and specificity. The invention of scanning
tunneling microscopy and atomic force microscopy has opened up the possibility of addressing and manipulating individual atoms
and molecules. Realization of the power of self-assembly principles has opened a novel approach for designing and assembling
molecular structures with desired intricate architecture. The utility of molecules such as DNA as a three-dimensional, high-density
memory element and its capability for molecular computing have been fully recognized but not yet realized. More time and effort
are necessary before devices that can transcend existing ones will become easily available. An overview of the current trends
that are envisaged to give rich dividends in the next millen-nium are discussed. 相似文献
98.
Platt M Muthukrishnan G Hancock WO Williams ME 《Journal of the American Chemical Society》2005,127(45):15686-15687
The conjugation of 14 nm diameter CoFe2O4 nanoparticles to the surface of biotinylated microtubules enables their manipulation with externally applied magnetic fields of small, permanent NdFeB magnets. Microtubules are selectively patterned on kinesin motor-modified glass surfaces in coparallel arrays that mimic the orientation of the magnetic field lines over millimeter distances. The magnetic field is simultaneously used to increase surface loading of microtubules. We demonstrate that motility across the kinesin motor surface is retained following magnetic functionalization of the microtubules, while gliding speed is dependent on loading level of the neutravidin linker as well as magnetic nanoparticles. 相似文献
99.
100.
Visweswara Rao Garimella Sridhar Yeleswarapu Hela Pamidipati Gayatri Padhi Trilochan Anipindi Nageswara Rao 《Transition Metal Chemistry》1999,24(5):566-570
The kinetics of substitution of Fe(tptz)2+2 by 2,2-bipyridine and 1,10-phenanthroline have been investigated in acetate buffers in the 3.6–5.6pH range employing stopped-flow spectrophotometry. These reactions are very fast and complete within 5s. The rate of substitution is linearly dependent on [phen] and [bpy]2, and increases with the increase in pH. Suitable mechanisms have been proposed involving the unprotonated form of the entering ligand, viz. bipyridine/phenanthroline as the reactive species. The pKa values of bipyridine and phenanthroline, determined from the kinetic data, are in agreement with the literature values. It is concluded that the substitutions of iron(II)-diimine complexes also occur by an associative mechanism. 相似文献